The present invention relates generally to a flexible, plastic composition and to the method for making and using such a plastic composition and containers thereof, wherein the plastic is capable of suppressing the hemolysis of red blood cells stored in containers made of the plastic composition.
Currently, the most widely used material for blood and blood component containers is polyvinyl chloride (PVC), with a sufficient amount of plasticizer added to soften the otherwise brittle 15 PVC. Plasticizers from the group of phthalate esters, and, in particular, di-2-ethylhexylphthalate (DEHP), have often been used in combination with the PVC resins. Although the use of DEHP plasticizer with plastic blood bags has generally worked satisfactorily, it is not without certain drawbacks.
As mentioned above, the rigid nature of PVC requires that it be softened with a plasticizer. However, it has been found that a small amount of plasticizer will leach into red blood cells stored within plasticized bags. Although no adverse physiological effects have been detected in patients receiving blood from DEHP plasticized containers, it is nonetheless desirable to minimize exposure of the patient to compounds not normally found in the body such as DEHP.
On the other hand, it is known in the prior art that the presence of DEHP has a beneficial effect on red blood cells stored within containers plasticized with DEHP. Specifically, red blood cells stored within containers plasticized with DEHP and perhaps other plasticizers such as triethylhexyltrimellitate (TEHTM) exhibit a much lower level of hemolysis than red blood cells stored in plasticizer-free containers, (see U.S. Pat. No. 4,507,387, col. 3, lines 6-28. ).
These known effects of DEHP have been utilized in the manufacture of multiple bag systems currently employed in blood storage and processing. Multi-bag systems usually include two or more bags wherein, through centrifuging and separation, each bag ultimately contains a different blood component, for example, red blood cells, blood platelets, and plasma. Since hemolysis is a measure of the destruction of red blood cells, it has been recognized that the red blood cell container may include a plasticizer to reduce hemolysis, while at the same time, the bags containing the other blood components, such as plasma or platelets, ought to be plasticizer free to reduce unnecessary exposure to DEHP. While such multi-bag systems have definite advantages, the need for containers made of different materials requires heightened quality control efforts and results in more expensive manufacturing costs.
As a result, the prior art discloses several efforts to develop plastic materials or bag constructions suitable for storing blood (and the various blood components) and exhibiting the antihemolytic effect of DEHP-plasticized polyvinyl chloride. See, e.g., U.S. Pat. No. 4,300,599.
One such effort described in U.S. Pat. No. 4,301,800 is to combine a plasticizer-free outer bag with a plasticized insert. Other prior art includes U.S. Pat. No. 4,507,387 which describes a combination of plasticizers, one of which, DEHP, leaches and the other of which did not leach.
Additionally, U.S. Pat. No. 4,140,162 describes a plasticizer-free polyolefin, which is said to be a suitable, flexible, autoclavable, chlorine-free material with excellent gas (O.sub.2 and CO.sub.2) permeability characteristics for storing blood and the various blood components, although in the absence of plasticizer, hemolysis of the red blood cells remains relatively higher than preferred.
The prior art has also described further plasticizers said to be compatible with PVC used in blood transfer and storage bags. U.S. Pat. Nos. 4,710,532 and 4,711,922, for example, suggest that citrate esters used as plasticizers for PVC are more easily metabolized by the body than DEHP.
Despite these efforts, the prior art has not been able to provide a flexible, chlorine-free composition suitable for use as a blood bag and capable of suppressing hemolysis of red blood cells stored within the bag, without the drawbacks associated with DEHP.
Accordingly, a general object of the present invention is to provide a plastic composition which does not suffer from the drawbacks described above.